The No.1 Website for Pro Audio
OM1 - What's it about?
Old 2 weeks ago
  #511
Here for the gear
 

I did a shootout between the OM1's with Shapeways APE spheres (https://www.shapeways.com/product/5K...line-audio-om1) and the following:

Beyerdynamic MC930's
NT-5's
NT-5's with NT45-o omni capsules
Pics attached.

This was a test recording with some new equipment, placement, and setup I wanted to try during my church job's weekly rehearsals. Reference pictures below. Measurements are: 18" between cardioids, 22" between omnis, all mics juuuust shy of 90-degrees wide, and pitched downward around 15-20 degrees. I wanted to get the NT45-o's capsules in line with the OM1's, but the spheres (and crowded mic bar) prevented that, so I had to go with those capsules up above like you see in the pictures.

Main array was ~16/17' high (more like 14-15' with the singers' location a bit higher than the floor the mic stand is on) and 15' away from the front edge of the group. The choir stands in the antiphonal pews on either side of the nave, facing each other. The space is huge, with tile floor, plaster walls, shallow A-frame roof, and big arcades on either side.

Signal flow was real simple: Mic of choice > Zoom F8

All samples are normalized to -24 LUFS. 44.1kHz dithered down to 16 bits, then transcoded to MP3 (didn't discover the file size limit until I tried posting!). No other processing to speak of.

Observations:

The APE spheres do a nice job of giving these mics "point" without robbing them of lushness, especially compared against both NT-5 pairs. I was kind of blown away by how well the spheres do in "cardioid-ifying" the OM1's, especially in comparing them to the "reach" the cardioid mics have in these samples. By comparison they're still a little "dark," but with a space with more early reflections than this one (which is huge, cold, and frankly kind of unmusical), I think they'd probably be the ones I reach for first. I think the NT45-o's do a nice job giving definition to the quieter sections, but become harsh in loud sections. I think the OM1's the most musical of the four pairs here.

Here's a neat thing I discovered: If I normalize all the source material to equal loudness, then mix an omni with a cardioid unity gain, the result becomes darker as the high frequency content starts to interfere between the two differently-spaced stereo pairs. Mixing one 6dB or more lower, or filtering out the top end of one of the two pairs, fixes the issue. I've been using this 4-mic array for years and never noticed that until now!
Old 2 weeks ago
  #512
Lives for gear
 
jpgerard's Avatar
Hmmm, I'd be more interested in a A/B of an OM1 with and without the sphere... but this is a cool test clearly showing the different mics behaviors.
Old 2 weeks ago
  #513
Here for the gear
 

Yeah totally... I really wanted to make that happen, but there was just never a window in the rehearsal for me to run down and switch the spheres out. Kinda bummed out about that, but I'll see if I can't make that happen on a future rehearsal. If I do, I'll be sure to post back.
Old 2 weeks ago
  #514
Lives for gear
 
jpgerard's Avatar
NO worries but I know (got that question several times) that many OM1 users wonder if the spheres are useful or at least how they change the polar and freq. responses. Thanks for your efforts!
Old 1 week ago
  #515
Lives for gear
Quote:
Originally Posted by SG_OC View Post
Yeah totally... I really wanted to make that happen, but there was just never a window in the rehearsal for me to run down and switch the spheres out. Kinda bummed out about that, but I'll see if I can't make that happen on a future rehearsal. If I do, I'll be sure to post back.
Yes, that's a comparison (with/without spheres) I'm sure many here would be interested in !

Another experimental variation could be comparing an OM-1 plus spheres pair angled out at 90* on the bar, versus both (also spheres) pointing directly ahead....in terms of stereo imaging, amount of perceived centre fill, etc

A Decca Tree with 5 'sphericaled' OM-1's (central 3 tree + 2 flanks/outriggers) is yet another experiment waiting to occur !

I wish Shapeways made a 30mm diameter ball option also, allowing a bit of choice in how much HF boost/directionality gets applied ? Maybe that's as simple as directing the request to Shapeways, as it would be a trivial change to the drive specs of the 3D printer to create one (and cheaper too, as less plastic is required !)

Given that the OM-1 has a tapered nose, I'm curious as to how they get the sphere to stay in place on the mic...since the natural tendency would be for it to slide off, if the mic is pointed downwards !

Do they incorporate some small 'teeth' or splines on the inside bore of the sphere, to grip against the tapered mic body ? Does it feel secure to you...or something that could fall off onto a conductor's or chorister's head during a concert ?
Old 1 week ago
  #516
Lives for gear
 

Quote:
Originally Posted by studer58 View Post
Given that the OM-1 has a tapered nose, I'm curious as to how they get the sphere to stay in place on the mic...since the natural tendency would be for it to slide off, if the mic is pointed downwards !
According to their website, the first generation of those spheres fit so tightly that people had trouble getting them off! They made the second generation slightly looser. I don't know how they make them stick, but it sounds like they stick.
Old 1 week ago
  #517
Quote:
Originally Posted by bradh View Post
According to their website, the first generation of those spheres fit so tightly that people had trouble getting them off! They made the second generation slightly looser. I don't know how they make them stick, but it sounds like they stick.
I don't own the spheres personally (yet!) but a school I work at does (the second gen ones) for their trio of OM-1s (used mostly in Decca tree arrays for outside broadcast applications), and they've got little splines on the inside to help them achieve a good push fit. We've not known them fall off, and there is also some adjustability in how much of the end of the mic pokes out of the sphere.
Old 1 week ago
  #518
Gear Addict
 
voltronic's Avatar
 

Quote:
Originally Posted by tenorfran View Post
...there is also some adjustability in how much of the end of the mic pokes out of the sphere.
That sounds like they may have created a new problem by solving the old one. As I understand it, the surface of an APE sphere should be as close as possible to the same plane as the mic diaphragm.
Old 1 week ago
  #519
Here for the gear
 

Y'all are giving me lots of testing configurations to try out! Will get to as many of these as possible. I can't record every rehearsal (my boss is pretty strict about interruptions) but I've got it all on my to-do now.

Francis speaks the truth - this revision of the spheres has little "legs" inside that grip the mic body firmly. I wouldn't have a worry about them falling off in any mounting orientation, nor having difficulty getting them off when loading out. This revision also has a much nicer, rounder finish to the sphere surface than the polygonal finish you see in the Shapeways thumbnail. I doubt that makes much of an acoustic difference, but it certainly looks nicer. Pic attached for reference.

Voltronic, I definitely think you're right about the concern. The sphere curvature *should* be in-line with the capsule. These spheres seem machined juuuuust a little bit large, such that the capsule ends up protruding about 1mm out from where the sphere surface would be. That's an estimated measurement by-eye. I was thinking about slipping the spheres down slightly so they'd be perfectly in-line, but I chose not to do it because it creates a very, very small gap around the mic body and the capsule-end opening. I was concerned about audible standing waves from within the spheres reaching the capsules, and figured letting the capsule out by 1mm was the lesser of two evils. More tests are in order, I wager.

Thanks for all the discussion, fellas.
Attached Thumbnails
OM1 - What's it about?-om1-sphere-splines.jpg  
Old 1 week ago
  #520
Lives for gear
A dilemma with several mics is knowing just where the diaphragm is located....typically it will have a screen or mesh above it to prevent fingers etc damage, but just how far below that is the actual capsule surface....we often can't be sure ?

Ideally, theoretically, the capsule surface would be be exactly level with the sphere surface ( or at as close as practicable) but I'm sure in some cases the capsule is quite a bit lower down in the mic's outer tube.

Does this matter..diffraction/interference effects ? Gaps between the bore hole in the sphere and the outer mic body diameter ? How about adding a thin rubber gasket ring, which may protrude above the sphere surface 0.5mm or less, to assist in sealing ?

These are the stuff of GS addicts' sleepless nights....

Thank you for the photo of the sphere, the finish does look smoother than previous pics on the Shapeways website. I've seen many pics of earlier such spheres from the established giants of the mic world, and most seem to have a hard, glossy outer finish....similar to a billiard/pool game ball.

I'd be inclined to apply several layers of a similar hard-coating lacquer to the sphere outer surface...once it were proven there was no adverse chemical reaction between the paint/lacquer and the 3D plastic ! That could help with the sphere's durability too.
Old 1 week ago
  #521
Gear Addict
 
voltronic's Avatar
 

Quote:
Originally Posted by studer58 View Post
A dilemma with several mics is knowing just where the diaphragm is located....typically it will have a screen or mesh above it to prevent fingers etc damage, but just how far below that is the actual capsule surface....we often can't be sure ?

Ideally, theoretically, the capsule surface would be be exactly level with the sphere surface ( or at as close as practicable) but I'm sure in some cases the capsule is quite a bit lower down in the mic's outer tube.
Yes, that's exactly what I was getting at. I'm sure the ever-helpful JP might be willing to ask Roger exactly where the diaphragm sits.

Quote:
Originally Posted by studer58 View Post
Thank you for the photo of the sphere, the finish does look smoother than previous pics on the Shapeways website. I've seen many pics of earlier such spheres from the established giants of the mic world, and most seem to have a hard, glossy outer finish....similar to a billiard/pool game ball.
I believe Delrin is what Schoeps, DPA, et al use. Some people have suggested using drilled wood spheres as a DIY solution, but I have never actually seen someone attempt it.
Old 1 week ago
  #522
Lives for gear
 
jpgerard's Avatar
Problem being that you can't have it perfectly parallel with the surface of the sphere anyway but what you want to avoid is a protrusion. Meaning that with the OM1 only the very tip of the mic should be flush with the sphere surface. The diaph. sits right behind the front end, as close as practically possible (1.5mm perhaps?).
Old 1 week ago
  #523
Lives for gear
Does it actually 'do' anything? I mean, I've tried 40mm wooden spheres on oktava 012 omni and didn't notice much change [even though these have some HF lift].
AFAIK the use of a sphere was supposed for diffuse field equalized omnis, working on their [exaggerated] high frequencies.
Old 1 week ago
  #524
Lives for gear
 
jpgerard's Avatar
They have an effect, whether you find it useful or not - is up to you. Roger and I don't recommend using the OM1 with such attachment as it ruins the linearity of the mic which is why they are so popular in the first place. However, those looking for a cheap M50 of sorts, find the sphere interesting.
Old 1 week ago
  #525
Gear Addict
 

Quote:
Originally Posted by jpgerard View Post
They have an effect, whether you find it useful or not - is up to you. Roger and I don't recommend using the OM1 with such attachment as it ruins the linearity of the mic which is why they are so popular in the first place. However, those looking for a cheap M50 of sorts, find the sphere interesting.
Just to check my understanding of this discussion...

So, adding the spheres to the OM1 changes the directional characteristics (desired if using a tree), but also adversely affects the linearity? Would that refer to the frequency response?

Thank you.

DG
Old 1 week ago
  #526
Linearity refers to frequency response, polar response, and phase response.

What makes the sphere such an effective tool is how it modifies the characteristic of whatever mic it is attached to in a predictable and musical way, even if not quite the epitome of “linear” (see the upper octaves of the polar response, for example).

In short, modifying the linearity is entirely the point of using the sphere, and the effect shouldn’t be any more adverse than using a sphere on any other quality omnidirectional sdc.

Quote:
Originally Posted by dgpretzel View Post
Just to check my understanding of this discussion...

So, adding the spheres to the OM1 changes the directional characteristics (desired if using a tree), but also adversely affects the linearity? Would that refer to the frequency response?

Thank you.

DG

Last edited by king2070lplaya; 1 week ago at 08:43 AM..
Old 1 week ago
  #527
Lives for gear
 
jpgerard's Avatar
Yep, sums it up. It does shuffle everything, it doesn't just act as an "acoustical lens", it definitely alters the freq. response. Google it, there articles including one from Neumann with graphs based ont he M50 (or maybe TLM50, I don't remember).
Old 4 days ago
  #528
Lives for gear
For a parallel, look up baffle step compensation for speakers.

Here's a nice little article by Rod Elliott - https://sound-au.com/bafflestep.htm

Applying that, it's pretty straightforward to figure out how adding a sphere to an omni mic will change things.

Chris
Topic:
Post Reply

Welcome to the Gearslutz Pro Audio Community!

Registration benefits include:
  • The ability to reply to and create new discussions
  • Access to members-only giveaways & competitions
  • Interact with VIP industry experts in our guest Q&As
  • Access to members-only sub forum discussions
  • Access to members-only Chat Room
  • Get INSTANT ACCESS to the world's best private pro audio Classifieds for only USD $20/year
  • Promote your eBay auctions and Reverb.com listings for free
  • Remove this message!
You need an account to post a reply. Create a username and password below and an account will be created and your post entered.


 
 
Slide to join now Processing…
Thread Tools
Search this Thread
Search this Thread:

Advanced Search
Forum Jump
Forum Jump